During pipe laying it may be necessary to abandon a pipeline and recover it later. For example, a pipeline may need to be abandoned because of a failure during the laying process (for example a wet-buckle may occur, causing a flooded pipeline). When the pipeline becomes flooded, the tensional load of the pipeline may significantly increase.
Conventionally, abandonment and recovery of a flooded pipeline is carried out by a method such as: welding an abandonment/recovery head (A/R head) onto the end of the pipeline being laid; connecting a plurality of A/R winches and sheaves to the head; transferring pipeline tension from the pipeline tensioning arrangement on the laying vessel that is used during normal laying, to the winches; lowering the pipeline using the winches and laying the pipeline and A/R head on the seabed.
Use of this conventional A/R system causes problems. The total capacity of the A/R winches needs to be sufficient to be able to lower the flooded pipeline; this necessitates a plurality of winches, and/or one or more winches of especially high capacity. Using multiple winches and sheaves can also be complex, and difficult to control.
It is an object of the invention to provide a method and apparatus of laying a pipeline which overcomes or at least mitigates the above-mentioned problems.